U.S. patent application number 14/581529 was filed with the patent office on 2015-04-23 for evaporative emission control.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Scott A. Bohr, Mark Bunge, Niels Christopher Kragh, Russell Randall Pearce, Mark W. Peters.
Application Number | 20150107562 14/581529 |
Document ID | / |
Family ID | 49475655 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150107562 |
Kind Code |
A1 |
Pearce; Russell Randall ; et
al. |
April 23, 2015 |
EVAPORATIVE EMISSION CONTROL
Abstract
A method for operating a fuel system is disclosed. The method
includes sequentially purging fuel vapors from each of a plurality
of regions of a canister. Purging a region includes opening an air
inlet valve associated with that region and maintaining air inlet
valves associated with each other region closed to direct fuel
vapors to at least one purge outlet.
Inventors: |
Pearce; Russell Randall;
(Ann Arbor, MI) ; Kragh; Niels Christopher;
(Commerce Township, MI) ; Bohr; Scott A.; (Novi,
MI) ; Bunge; Mark; (Dearborn, MI) ; Peters;
Mark W.; (Wolverine Lake, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
49475655 |
Appl. No.: |
14/581529 |
Filed: |
December 23, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13466528 |
May 8, 2012 |
8919327 |
|
|
14581529 |
|
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Current U.S.
Class: |
123/520 |
Current CPC
Class: |
F02D 41/004 20130101;
F02D 41/003 20130101; F02D 19/0621 20130101; F02M 25/0854 20130101;
F02M 25/0872 20130101; F02M 25/089 20130101; F02D 41/0032 20130101;
F02M 25/0836 20130101 |
Class at
Publication: |
123/520 |
International
Class: |
F02D 41/00 20060101
F02D041/00; F02M 25/08 20060101 F02M025/08 |
Claims
1. A method for operating a fuel system comprising: sequentially
purging fuel vapors from each of a plurality of regions of a
canister, where purging a region includes opening an air inlet
valve associated with that region and maintaining air inlet valves
associated with each other region closed to direct fuel vapors to
at least one purge outlet until a fuel fraction of combustion gases
exhausted from cylinders is less than a set point.
2. The method of claim 1, wherein sequentially purging is performed
responsive to a fuel tank filling event.
3. The method of claim 1, wherein fuel vapors are purged from each
region until the fuel fraction becomes less than the set point, and
when the plurality of regions are purged the sequence is
repeated.
4. The method of claim 1, wherein the canister includes four
regions and four air inlet valves corresponding to the four
regions.
5. The method of claim 4, wherein two pairs of air inlet valves are
located on opposing sides of the canister.
6. The method of claim 1, wherein the canister includes two purge
outlets located on opposing sides of the canister.
7. The method of claim 1, wherein the at least one purge outlet is
located on a different side of the canister from a plurality of air
inlet valves.
8. A fuel system comprising: a fuel tank; a canister for storing
fuel vapors including: a canister inlet fluidly coupled with the
fuel tank; a plurality of air inlet valves associated with a
plurality of regions of the canister; and at least one purge outlet
fluidly coupled with an intake manifold; and a controller including
a processor and computer readable medium having instructions that
when executed by the processor: during purging of the canister,
increase vacuum in a designated region relative to each other
region in the canister to direct fuel vapors in the designated
region to the at least one purge outlet, wherein the canister
includes four regions and four air inlet valves corresponding to
the four regions, and wherein two pairs of air inlet valves are
located on opposing sides of the canister.
9. The fuel system of claim 8, wherein the controller increases
vacuum in the designated region responsive to a fuel tank filling
event.
10. The fuel system of claim 8, wherein vacuum is increased by
opening an air inlet valve associated with the designated region
and closing air inlet valves associated with each other region.
11. The fuel system of claim 8, wherein vacuum is increased in the
designated region until a fuel fraction of combustion gases
exhausted from cylinders becomes less than a set point.
12. The fuel system of claim 8, wherein the canister includes two
purge outlets located on opposing sides of the canister.
13. The fuel system of claim 8, wherein the at least one purge
outlet is located on a different side of the canister from a
plurality of air inlet valves.
14. A canister for storing fuel vapors comprising: a canister inlet
fluidly coupled with a fuel tank; a first purge outlet and a second
purge outlet fluidly coupled with an intake manifold, the first
purge outlet and the second purge outlet being located on opposing
sides of the canister; a plurality of air inlet valves associated
with a plurality of regions of the canister, each of the plurality
of air inlet valves being individually operable to purge fuel
vapors from an associated region to the first purge outlet or the
second purge outlet; and a controller including a processor and
computer readable medium having non-transitory instructions stored
in memory that when executed by the processor: sequentially purge
fuel vapors from each of the plurality of regions of the canister,
where purging a region includes opening an air inlet valve
associated with that region and maintaining air inlet valves
associated with each other region closed to direct fuel vapors to
the at least one purge outlet, wherein the plurality of air inlet
valves includes two pairs of air inlet valves located on opposing
sides of the canister.
15. The fuel system of claim 14, wherein the first and second purge
outlets are located on opposing sides of the canister, and on
different sides of the canister from the plurality of air inlet
valves.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/466,528, entitled "EVAPORATIVE EMISSION
CONTROL," filed on May 8, 2012, the entire contents of which are
hereby incorporated by reference for all purposes.
BACKGROUND AND SUMMARY
[0002] Vehicles may be fitted with evaporative emission control
systems to reduce the release of fuel vapors to the atmosphere. For
example, vaporized hydrocarbons (HCs) from a fuel tank may be
stored in a fuel vapor canister packed with an adsorbent which
adsorbs and stores the fuel vapors. At a later time, when the
engine is in operation, the evaporative emission control system
allows the fuel vapors to be purged into the engine intake manifold
from the fuel vapor canister to be consumed during combustion.
[0003] In one example described in U.S. Pat. No. 5,398,660, a fuel
vapor canister includes a plurality of purge valves and a plurality
of air inlet valves. During operation of the engine, all of the
purge valves and the air inlet valves may be opened to supply a
negative pressure from an engine air induction passage to within
the canister. As a result of the supply of the vacuum, fuel vapor
is purged to the intake manifold of the engine from the fuel vapor
canister.
[0004] However, the inventors herein have recognized issues with
the above approach. For example, in engine applications that
operate with low vacuum air induction, by opening all air inlet and
purge valves of the fuel vapor canister at the same time, a small
amount of vacuum may be created in the fuel vapor canister.
Accordingly, the amount of time it takes for the fuel vapor
canister to be purged may be substantial. More particularly, in
hybrid electric vehicle (HEV) applications, the engine run time may
be shorter than the amount of time it takes to purge the fuel vapor
canister with low vacuum.
[0005] Thus, in one example, the above issues may be addressed by a
method for operating a fuel system comprising: sequentially purging
fuel vapors from each of a plurality of regions of a canister.
Specifically, purging a region of the canister may include opening
an air inlet valve associated with that region and maintaining air
inlet valves associated with each other region of the canister
closed in order to direct fuel vapors to at least one purge outlet
of the canister.
[0006] In one example, a region of the canister may be purged until
a fuel fraction of combustion gases exhausted from the cylinders is
less than a set point. Once a region has been purged to the set
point, the associated air inlet valve may be closed and an air
inlet valve associated with a next region in the sequence may be
opened while maintaining each of the other air inlet valves closed
to purge that region.
[0007] By opening one air inlet valve at a time, air flow through
the region of the canister associated with that air inlet valve may
be increased to more quickly purge fuel vapors from that region to
meet the set point. In this way, the amount of time to purge the
canister may be reduced relative to the approach where all valves
are opened at the same time. Moreover, the increased air flow may
purge the region more thoroughly relative to a purge approach with
lower air flow. In other words, the increased air flow may increase
the likelihood of attaining zero bleed emissions from the
canister.
[0008] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1 schematically shows an example of a hybrid propulsion
system according to an embodiment of the present disclosure.
[0010] FIG. 2 schematically shows an example of an engine and an
associated fuel system according to an embodiment of the present
disclosure.
[0011] FIG. 3 schematically shows an example of a fuel vapor
canister according to an embodiment of the present disclosure.
[0012] FIGS. 4-7 show an example of different regions of a fuel
vapor canister being sequentially purged.
[0013] FIG. 8 shows an example of a method for controlling a fuel
system according to an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0014] The present description relates to controlling evaporative
emissions in a vehicle. More particularly, the present disclosure
relates to fuel vapor purging by sequentially purging different
regions of a fuel vapor canister. By sequentially purging each
region of the fuel vapor canister one at a time, air flow through
that region may be increased to more quickly and thoroughly purge
that region relative to an approach where the entire canister is
purged all at once. Such an approach may be applicable to low
vacuum air induction engine applications. Furthermore, such an
approach may be applicable to hybrid electric vehicle (HEV)
applications and other applications with limited engine run
time.
[0015] FIG. 1 schematically shows an example of a vehicle system 1
according to an embodiment of the present disclosure. The vehicle 1
includes a hybrid propulsion system 12. The hybrid propulsion
system 12 includes an internal combustion engine 10 having one or
more cylinders 30, a transmission 16, drive wheels 18 or other
suitable device for delivering propulsive force to the ground
surface, and one or more motors 14. In this way, the vehicle may be
propelled by at least one of the engine or the motor.
[0016] In the illustrated example, one or more of the motors 14 may
be operated to supply or absorb torque from the driveline with or
without torque being provided by the engine. Accordingly, the
engine 10 may operate on a limited basis. Correspondingly, there
may be limited opportunity for fuel vapor purging to control
evaporative emissions. It will be appreciated that the vehicle is
merely one example, and still other configurations are possible.
Therefore, it should be appreciated that other suitable hybrid
configurations or variations thereof may be used with regards to
the approaches and methods described herein. Moreover, the systems
and methods described herein may be applicable to non-HEVs, such as
vehicles that do not include a motor and are merely powered by an
internal combustion.
[0017] FIG. 2 schematically shows an example of an engine system
100 according to an embodiment of the present disclosure. For
example, the engine system 100 may be implemented in the vehicle
system 1 shown in FIG. 1. The engine system 100 includes an engine
block 102 having a plurality of cylinders 104. The cylinders 104
may receive intake air from an intake manifold 106 via an intake
passage 108 and may exhaust combustion gases to an exhaust manifold
110 and further to the atmosphere via exhaust passage 112.
[0018] The intake passage 108 includes a throttle 114. In this
particular example, the position of the throttle 114 may be varied
by a controller 120 via a signal provided to an electric motor or
actuator included with the throttle 114, a configuration that is
commonly referred to as electronic throttle control (ETC). In this
manner, the throttle 114 may be operated to vary the intake air
provided to the plurality of cylinders 104. The intake passage 108
may include a mass air flow sensor 122 and a manifold air pressure
sensor 124 for providing respective signals MAF and MAP to the
controller 120.
[0019] An emission control device 116 is shown arranged along the
exhaust passage 112. The emission control device 116 may be a three
way catalyst (TWC), NOx trap, various other emission control
devices, or combinations thereof. In some embodiments, during
operation of the engine 100, the emission control device 116 may be
periodically reset by operating at least one cylinder of the engine
within a particular air/fuel ratio. An exhaust gas sensor 118 is
shown coupled to the exhaust passage 112 upstream of the emission
control device 116. The sensor 118 may be any suitable sensor for
providing an indication of exhaust gas air/fuel ratio such as a
linear oxygen sensor or UEGO (universal or wide-range exhaust gas
oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a
NOx, HC, or CO sensor. It will be appreciated that the engine
system 100 is shown in simplified form and may include other
components.
[0020] A fuel injector 132 is shown coupled directly to the
cylinder 104 for injecting fuel directly therein in proportion to a
pulse width of a signal received from the controller 120. In this
manner, the fuel injector 132 provides what is known as direct
injection of fuel into the cylinder 104. The fuel injector may be
mounted in the side of the combustion chamber or in the top of the
combustion chamber, for example. Fuel may be delivered to the fuel
injector 132 by a fuel system 126. In some embodiments, cylinder
104 may alternatively or additionally include a fuel injector
arranged in intake manifold 106 in a configuration that provides
what is known as port injection of fuel into the intake port
upstream of the cylinder 104.
[0021] The fuel system 126 includes a fuel tank 128 coupled to a
fuel pump system 130. The fuel pump system 130 may include one or
more pumps for pressurizing fuel delivered to the injectors 132 of
the engine 100, such as the fuel injector 132. While only a single
injector 132 is shown, additional injectors are provided for each
cylinder. It will be appreciated that fuel system 126 may be a
return-less fuel system, a return fuel system, or various other
types of fuel system.
[0022] Vapors generated in the fuel system 126 may be directed to
an inlet of a fuel vapor canister 134 via a vapor recovery line
136. The fuel vapor canister may be filled with an appropriate
adsorbent to temporarily trap fuel vapors (including vaporized
hydrocarbons) during fuel tank refilling operations and "running
loss" (that is, fuel vaporized during vehicle operation). In one
example, the adsorbent used is activated charcoal. The fuel vapor
canister 134 may be fluidly coupled to a vent line 138 via a
plurality of air inlet valves 140. The plurality of air inlet
valves 140 may be independently operable to fluidly couple
different regions of the fuel vapor canister 134 with the vent line
138. Under some conditions, the vent line 138 may route gases out
of the fuel vapor canister 134 to the atmosphere, such as when
storing, or trapping, fuel vapors of the fuel system 126.
Additionally, the vent line 138 may also allow fresh air to be
drawn into the fuel vapor canister 134 when purging stored fuel
vapors through one or more purge outlets of the fuel vapor canister
to the intake manifold 106 via a purge line 142. A purge valve 144
may be positioned in the purge line and may be controlled by the
controller 120 to regulate flow from the fuel vapor canister to the
intake manifold 106. A vent valve 146 may be positioned in the vent
line and may be controlled by the controller 120 to regulate the
flow of air and vapors between the fuel vapor canister 134 and the
atmosphere.
[0023] The controller 120 is shown in FIG. 1 as a microcomputer,
including microprocessor unit 148, input/output ports, a computer
readable storage medium 150 for executable programs and calibration
values (e.g., read only memory chip, random access memory, keep
alive memory, etc.) and a data bus. Storage medium read-only memory
150 can be programmed with computer readable data representing
instructions executable by the processor 148 for performing the
methods described below as well as other variants that are
anticipated but not specifically listed.
[0024] The controller 120 may receive information from a plurality
of sensors 152 of the engine system 100 that correspond to
measurements such as inducted mass air flow, engine coolant
temperature, ambient temperature, engine speed, throttle position,
manifold absolute pressure signal, air/fuel ratio, fuel fraction of
intake air, fuel tank pressure, fuel canister pressure, etc. Note
that various combinations of sensors may be used to produce these
and other measurements. Furthermore, the controller 120 may control
a plurality of actuators 154 of the engine 100 based on the signals
from the plurality of sensors 152. Examples of actuators 154 may
include air inlet valves 140, purge valve 144, vent valve 146,
throttle 114, fuel injector 132, etc.
[0025] In one example, the controller 120 includes computer
readable medium 150 having instructions that when executed by the
processor 148: sequentially purge fuel vapors from each of a
plurality of regions of the fuel vapor canister 134 in response to
a fuel tank filling event. In particular, purging a region may
include opening an air inlet valve associated with that region and
maintaining air inlet valves associated with each other region
closed to direct fuel vapors from that region to a purge outlet of
the fuel vapor canister 134. In other words, one air inlet valve
may be opened at a time during purging of a region. By opening one
air inlet valve at a time, air flow through the region of the fuel
vapor canister nearest to the open air inlet valve may be increased
relative to when all air inlet valves are open. The increased air
flow may more quickly and thoroughly purge fuel vapors from that
region. This may be particularly beneficial in low vacuum air
induction engine systems and engines having shortened run time,
such as with HEVs.
[0026] In one example, each region of the fuel vapor canister is
purged until a fuel fraction of combustion gases exhausted from the
cylinders is less than a set point. Once the set point for a region
is achieved, the corresponding air inlet valve may be closed and an
air inlet valve of the next region in the sequence may be opened
while maintaining the other air inlet valves closed to purge that
region, and so on until all regions of the fuel vapor canister are
purged. In some embodiments, when the plurality of regions of the
fuel vapor canister are purged the sequence may be repeated. In
some embodiments, the sequence may be repeated responsive to the
next fuel filling event. In some embodiments, the sequence may be
repeated based on changes in environmental conditions, such as a
change in temperature beyond a set point. It will be appreciated
that the regions of the fuel vapor canister may be purged according
to any suitable sequence without departing from the scope of the
present disclosure.
[0027] In one example, the controller includes a processor and
computer readable medium having instructions that when executed by
the processor: during purging of the canister, increase vacuum in a
designated region relative to each other region in the canister to
direct fuel vapors in the designated region to the at least one
purge outlet. Vacuum may be increased in the designated region by
opening an air inlet valve associated with the designated region
and closing air inlet valves associated with each other region. The
controller may increase vacuum in the designated region responsive
to a fuel tank filling event. Vacuum may be increased in the
designated region until a fuel fraction of combustion gases
exhausted from cylinders becomes less than a set point. Once the
designated region is purged to the set point, the controller may
designate another region for purging and increase the vacuum in
that region relative to the other regions to purge that region, and
so on until all regions are purged.
[0028] FIG. 3 schematically shows an example of a fuel vapor
canister 300 according to an embodiment of the present disclosure.
In one example, the canister 300 may be implemented in the engine
system 100 shown in FIG. 2. The canister 300 includes a canister
inlet fluidly coupled with a fuel tank (e.g., fuel tank 128 shown
in FIG. 2). The canister inlet 302 permits fuel vapors that escape
from the fuel tank to enter the canister 300 for storage. In one
example, the canister 300 is filled with activated charcoal to
store fuel vapors. In some embodiments, the canister may include
more than one canister inlet.
[0029] The canister 300 includes a first purge outlet 304 and a
second purge outlet 306 fluidly coupled with an intake manifold
(e.g., intake manifold 106 shown in FIG. 2). The first and second
purge outlets 304 and 306 permit fuel vapors to travel to the
intake manifold from the canister 300 during purging, so that the
fuel vapors can be consumed by combustion instead of being vented
to the atmosphere. The canister 300 includes a plurality of regions
308 (e.g., 1, 2, 3, 4) that may store fuel vapors. The plurality of
regions 308 may be sequentially purged one at a time according to a
fuel purging method discussed in further detail below. In the
illustrated embodiment, the first purge outlet and the second purge
outlet are located on opposing sides of the canister. Specifically,
the first purge outlet 304 is located on a first side 330 and the
second purge outlet is located on a second side 332 that opposes
the first side 330. The purge outlets may be positioned on opposing
sides in order to facilitate the purging of fuel vapors from the
different regions of the canister in substantially the same or
similar manner. In other words, no region is positioned farther
away from a purge outlet then any other region in the canister.
Accordingly, the amount of time it takes to purge each region may
be similar or substantially the same. It will be appreciated that
the canister may include any suitable number of purge outlets that
may be located in any suitable position on the canister without
departing from the scope of the present disclosure.
[0030] The canister 300 includes a plurality of air inlet valves
associated with the plurality of regions 308. In the illustrated
embodiment, the canister includes four regions and four air inlet
valves corresponding to the four regions. Specifically, a first air
inlet valve 312 controls air flow through a first air inlet 310 to
a first region; a second air inlet valve 316 controls air flow
through a second air inlet 314 to a second region; a third air
inlet valve 320 controls air flow through a third air inlet 318 a
third region; and a fourth air inlet valve 324 controls air flow
through a fourth air inlet 322 to a fourth region. Each air inlet
may be positioned such that during purging of a region air flows
from that air inlet through the region to the nearest purge
outlet.
[0031] In the illustrated embodiment, two pairs of air inlet valves
are located on opposing sides of the canister. Specifically, the
first air inlet valve 312 and the fourth air inlet valve 314 are
positioned on a side 326 and the second air inlet valve 316 and the
third air inlet valve 320 are positioned on a side 328 that opposes
side 326. Furthermore, the first and second purge outlets 304 and
306 are located on different sides of the canister from the
plurality of inlet valves. In this way, air flowing through any air
inlet valve flows through a corresponding region of the canister to
reach a purge outlet. In one example, a region corresponds to an
air inlet valve if air from the air inlet valve travels through the
region to reach a purge outlet. In some embodiments, the canister
300 may include a dividing wall 334 that may partially divide the
regions of the canister. The dividing wall 334 may help direct air
flow through a particular region during purging by at least
partially blocking access to other regions of the canister. It will
be appreciated that the canister may include any suitable number of
air inlet valves that may be located in any suitable position on
the canister without departing from the scope of the present
disclosure.
[0032] Each of the plurality of air inlet valves may be controlled
by controller 336. In one example, the controller 336 is the
controller 120 shown in FIG. 2. Each of the plurality of air inlet
valves may be individually operable by the controller 336 to purge
fuel vapors from an associated region to a purge outlet. In other
words, the controller 336 may be configured to open one air inlet
valve and close the other air inlet valves in order to purge a
particular region of the canister. FIGS. 4-7 show an example of
different regions of the fuel vapor canister 300 being sequentially
purged. In these examples, the sequence in which the regions of the
canister are purge is 1-4. Although it will be appreciated that any
suitable purging sequence may be implemented without departing from
the scope of the present disclosure.
[0033] FIG. 4 shows the first region being purged. Specifically,
the first air inlet valve is opened and the other air inlet valves
are closed so that air travels from the first air inlet valve,
through the first region, to the second purge outlet. Once the
first region is purged, for example, such that a fuel fraction is
less than a set point, the next region in the sequence may be
purged.
[0034] FIG. 5 shows the second region being purged. Specifically,
the second air inlet valve is opened and the other air inlet valves
are closed so that air travels from the second air inlet, through
the second region, to the second purge outlet. Once the second
region is purged, for example, such that a fuel fraction is less
than a set point, the next region in the sequence may be
purged.
[0035] FIG. 6 shows the third region being purged. Specifically,
the third air inlet valve is opened and the other air inlet valves
are closed so that air travels from the third air inlet, through
the third region, to the first purge outlet. Once the third region
is purged, for example, such that a fuel fraction is less than a
set point, the next region in the sequence may be purged.
[0036] FIG. 7 shows the fourth region being purged. Specifically,
the fourth air inlet valve is opened and the other air inlet valves
are closed so that air travels from the fourth air inlet, through
the fourth region, to the first purge outlet. Once the fourth
region is purged, for example, such that a fuel fraction is less
than a set point, purging may end or the sequence may be
repeated.
[0037] FIG. 8 shows an example of a method 800 for controlling a
fuel system according to an embodiment of the present disclosure.
For example, the method 800 may be performed by the controller 120
shown in FIG. 2 or the controller 336 shown in FIG. 3
[0038] At 802, the method 800 includes determining operating
conditions. Determining operating conditions may include receive
signals from sensors indicative of various operating conditions,
such as air/fuel ratio, fuel fraction, engine operation, fuel tank
pressure, fuel tank filling event, etc.
[0039] At 804, the method 800 includes determining whether a fuel
tank filling event has occurred. If a fuel filling event has
occurred, then the method 800 moves to 806. Otherwise, the method
800 returns to 804.
[0040] At 806, the method 800 includes determining whether the
engine is running If the engine is running, then the method 800
moves to 8-6. Otherwise, the method 800 returns to 806.
[0041] At 808, the method 800 includes sequentially purging a
plurality of regions of a fuel vapor canister. The canister may be
purged responsive to a fuel filling event because when the fuel
tank is filled with liquid fuel, fuel vapors residing in the fuel
tank may be pushed into the fuel vapor canister to fill the fuel
vapor canister. Moreover, the canister may be purged when the
engine is running so that fuel vapors can be used for combustion
instead of being vented to the atmosphere. More particularly, at
810, the method 800 includes designating a region of the canister
for purging.
[0042] At 812, the method 800 includes opening an air inlet valve
associated with the designated region.
[0043] At 814, the method 800 includes closing other air inlet
valves of the canister. Note closing may include maintaining valves
in a closed state, so that one air inlet valve is open at a time.
By opening the air inlet valve associated with the designated
region and closing the other air inlet valves, vacuum in the
designated region may be increased relative to the other regions of
the canister. The vacuum may be increased in the designated region
to direct air flow from the open air inlet valve, through the
designated region, to a closest purge outlet to purge fuel vapors
from the designated region.
[0044] At 816, the method 800 includes determining if a fuel
fraction of combustion gases exhausted from the cylinders is less
than a set point. If the fuel fraction is less than the set point,
then the method moves to 818. Otherwise, the method returns to
816.
[0045] At 818, the method 800 includes determining if all regions
of the canister have been purged. If all regions of the canister
have been purged, then the method returns to other operations.
Otherwise, the method moves to 820.
[0046] At 820, the method 800 includes designating the next region
in the sequence to be purged. Once the next region has been
designated steps 812-814 are repeated for that region, and so on
until all regions of the canister have been purged.
[0047] By sequentially purging each region of the fuel vapor
canister one at a time, air flow through that region may be
increased to more quickly and thoroughly purge that region relative
to an approach where the entire canister is purged all at once.
Such an approach may be applicable to low vacuum air induction
engine applications. Furthermore, such an approach may be
applicable to hybrid electric vehicle (HEV) applications and other
applications with limited engine run time.
[0048] Note that the example control routines included herein can
be used with various engine and/or vehicle system configurations.
The specific routines described herein may represent one or more of
any number of processing strategies such as event-driven,
interrupt-driven, multi-tasking, multi-threading, and the like. As
such, various acts, operations, or functions illustrated may be
performed in the sequence illustrated, in parallel, or in some
cases omitted. Likewise, the order of processing is not necessarily
required to achieve the features and advantages of the example
embodiments described herein, but is provided for ease of
illustration and description. One or more of the illustrated acts
or functions may be repeatedly performed depending on the
particular strategy being used. Further, the described acts may
graphically represent code to be programmed into the computer
readable storage medium in the engine control system.
[0049] It will be appreciated that the configurations and routines
disclosed herein are exemplary in nature, and that these specific
embodiments are not to be considered in a limiting sense, because
numerous variations are possible. For example, the above technology
can be applied to V-6, 1-4, 1-6, V-12, opposed 4, and other engine
types. Further, one or more of the various system configurations
may be used in combination with one or more of the described
diagnostic routines. The subject matter of the present disclosure
includes all novel and nonobvious combinations and subcombinations
of the various systems and configurations, and other features,
functions, and/or properties disclosed herein.
* * * * *